Everyone knows somewhat what shin splints are. Shin pain. Pretty basic. The cause is almost always excessive repetition and overuse. The problem is that shin splints can be any number of things- but if you've got the shin pain thing working for you, here's some of the probables:

Tibialis anterior strain:
This is probably the most common- so chances are you have it. You might not, but you probably do. The tibialis anterior is the muscle just slightly to the lateral side (outside) of your tibia (shin bone). It is the agonist in eversion (lifting up the end of your foot) and can easily be overused through any activity that requires movement (jogging, cardio classes, basketball, etc.) You can tell if this is the problem often by tenderness upon touch, flexion, and stretching the muscle. Most often, this is the problem, and it's the least severe and most easily healed of the seven. Ice and rest. That's about it. If you try to IBU profin it away and carry on as usual however, it won't be pretty. So let it heal. Keep off your rigorous schedule for a week and ice it two to three times per day for 20 minutes each. Elevating it wouldn't hurt either. When it's healed enough to be on it, doing heal walks a few days per week will build it up and help prevent it happening again. So walk around on your heals without letting your toes touch the ground for five minutes and it'll strengthen that right up.

Tibialis posterior strain or tendonitis:
This is a similar injury to the previous. The tibialis posterior's primary function is inversion (rolling the bottom of the foot inward). Because of this, it is consistently used for stabalization, trying to keep the ankle strait forward. Too much of that will lead to tendonitis or a strain. This usually happens in sports that require balance and stabilization with movement (i.e. not swimming or cricket). If resisted inversion or stretching the foot in an everted position (opposite of inversion) sends pain up the rear inside portion of the calf, that's probably what you've got. Rest and ice it for a week. Two to three times per day ice it for 20 minutes and keep off anything that bothers it.

Periosteitis:
This is the inflammation of the surface of a bone near where a tendon attaches. Usually you can tell if this is the problem if there is diffuse pain running up and down the tibia that's never really localized. If there's pain that's not really felt or increased when you tap the bone, this is probably what it is. It usually comes from increasing your training regimen or overall workload too rapidly. If you already have it, rest, elevate, compress, ice, and lightly stretch it. Lightly. Don't do any activity that bothers it, but light activity helps it heal faster, swimming or cycling or something like that.

Tibial stress fractures:
Alright. Stress fractures. One of the scary ones. It usually happens in the proximal (closest) third of the tibia. Usually 2 to 5 centimeters distal to the tibial tuberosity. So basically it's 2 to 5 centimeters down from that little bump below your patella. There's sometimes pain with resisted planter flexion or inversion, and just about always severe point tenderness. If this is you, be careful. Reduce your activity for pretty much a huge long time and go to the doctor to check it out. Depending on how bad it is it's possible that you may need to be casted.

Fibular stress fractures:
Not common. Tibial stress fractures happen. These pretty much don't. They exist because they're physically possible, but other than that I don't really need to write about them. You won't have one.

Recurrent chronic anterior compartment syndrome:
Okay. The anterior compartment of the leg is just a few muscles. tibialis anterior, extensor digitorum longus, extensor hallicus longus, and peroneus tertius. They're surrounded by this tough fascia sheathe that's a little hard to stretch or expand. During intense exercise those muscles could swell up with blood, and while the fascia doesn't expand you get to compress your nerves and vessels. Which is really neat because it hurts bad. It can also happen if your muscles grow faster than the sheathe, causing ischemia, necrosis, paresthesia, and pain in that little area there. The pain is only induced by activity and usually goes away afterwards and sometimes numbness or tingling is felt. Just go ahead and go to the doctor if this one is you, and let them know what you have. It's not horrid, but they'll be better at it than me.

Inflammation of the interosseous membrane:
This is the area between the tibia and fibula. It's this little ligament sheathe that pretty much just holds the the two together. A bunch of stress and overuse can inflame it. That's where the pain would be at. So go ahead and hit the doctor on this one too.